advice on garage electrics

[coticsam]

hello, im after some advice on a fault i have with my electrics in my garage. i moved into the house just over a year ago and the garage only have a light and a socket, the previous owner had already installed an armoured cable from the consumer unit under the stairs, through the garden into the garage into an old metal consumer with wire type fuses, my dad is a plumber but he has basic electrical knowledge from the electrical side of his job,boiler and electric showers etc, i had him install a new consumer unit, strip lights and multiple sockets and 2x 16a amp blue sockets. every thing is ok but the 16a sockets. i run a large mig and a plasma cutter which the manufacture say needs a 16A supply. with either machine set to half power it will trip the rcbo (i have a type c and b, the c will accept slightly more power before it trips) i dont even get to use the machine as it wil trip as soon as i pull the trigger not mid use, if i use a lower power setting its ok, i have been using a blue 16a to 3 pin plug adaptor to use the machines, have used both on full power without issues but this was only on short runs, prolonged use i think the 13a fuse would blow. i have a new welder in mind for heavier fabrication which needs a good supply so the plug adaptor will not work for this.
i have added details pictures bellow, hope someone could identify the problem, if its simple i will have my dad do it, if not i will get an electrican in. hope i dont get shot down in flames for any problems

this is the garage supply from the consumer unit under the stairs



the is the armoured cable leaving the consumer. i think the earthing is wrong and it should have a swa gland with metal box (not sure if this could cause fault) previous owner installed this.




this is the armoured cable going into the garage, he has used 2 wires from 4 core cable, he was a ground worker so think he just used what he could get his hands on. guessing the wires are just tucked inside the house consumer, i have not took the cover off to look.





after it comes out of that little plastic box it goes into this, not sure if its needed, in the past when i tested the type b socket this tripped and not the rcbo. this and the plastic box was installed by previous owner, we did the consumer and everything coming out of it.



from this into consumer unit, not sure if they all need to be rcbo, i just used what came with the unit (ebay)
the consumer unit has a earth wire going out into the ground outside garage, guessing it has a spike in the ground, this was fitted to the old consumer so we fitted to new one,



then to my sockets, b and c refusing to which type rcbo. they each have a single wire going to them were as the other sockets are on a ring main




hope someone can help

sam

 

[Richard Burns]

There are some significant worries with the installation you have shown, but without proper testing it would be difficult to determine whether they are dangerous.
Regarding your MIG/plasma cutter these can cause a very high peak current on starting that could be tripping out the circuit breaker part of the RCBO, because the C type takes more power than the B type this sounds likely, however welders / cutters can also generate transient earth currents depending on how the cables are arranged and this would trip the RCD side of the RCBO, however because the main RCD is not tripping I think this is less likely.
Without testing of the installation I would not be able to recommend any resolution for this as it would be dependent on the characteristics of the supply whether they were suitable.

 

[coticsam]

There are some significant worries with the installation you have shown, but without proper testing it would be difficult to determine whether they are dangerous.
Regarding your MIG/plasma cutter these can cause a very high peak current on starting that could be tripping out the circuit breaker part of the RCBO, because the C type takes more power than the B type this sounds likely, however welders / cutters can also generate transient earth currents depending on how the cables are arranged and this would trip the RCD side of the RCBO, however because the main RCD is not tripping I think this is less likely.
Without testing of the installation I would not be able to recommend any resolution for this as it would be dependent on the characteristics of the supply whether they were suitable.

Hi, thanks for your reply. What faults can you see with it?

 

[Richard Burns]

The size of the SWA is not clear but will be on the limit of current carrying capacity, or below it, for installation depending on the cable run.
The SWA is not earthed correctly on the armour, using a BS851 clamp is inappropriate and does not provide a good contact.
Because there is no gland in place the SWA will be supported by the connections in the CU.
The BS951 clamp does not appear to be labelled, and also appears to be loose.
Yellow is not an approved colour for use as an earthing conductor.
There appears to be a sealed water pipe just below the CU, not inherently dangerous but not a good place to terminate a water pipe.
The unused cores are not terminated safely to avoid inadvertent contact, and the use of 4 core is redundant, but could have usefully used the cores in parallel.
The electrical work done in the garage requires extensive inspection, testing and certification and legally requires notification to building control, these may have been done but I am not certain of that from your description.
Based on the previous work done the installation in the garage is a TT system which requires a quality level of earth from the external rod and if this was DIY done then it is unlikely to be well done and may present a danger to the installation.
I am assuming the green and yellow cable running beside the CU and RCD is going to the rod and not to the SWA armour, if it is from the armour then the system may not be TT in its entirety and would change the requirements for the installation.
The use of C type RCBOs in this situation may, based on the design of the installation, cause problems with compliance with the disconnection times for a short circuit, though the earth fault levels would be complied with by the use of the RCD parts, if the rod is suitable.
The cables for the 16A sockets do not appear to be sealed into the sockets which could allow contamination into the socket cable connections.

That is all I can anticipate at the moment, some of them may not be correct as I cannot assess the installation, but they do give rise to concern.

 

[coticsam]

The size of the SWA is not clear but will be on the limit of current carrying capacity, or below it, for installation depending on the cable run.

No idea on size
The SWA is not earthed correctly on the armour, using a BS851 clamp is inappropriate and does not provide a good contact.
Because there is no gland in place the SWA will be supported by the connections in the CU.
The BS951 clamp does not appear to be labelled, and also appears to be loose.
I was aware that it needed a correct gland to be fitted to armour.there is a label on the clamp its just folded around the back, clamp is also tight

Yellow is not an approved colour for use as an earthing conductor.


There appears to be a sealed water pipe just below the CU, not inherently dangerous but not a good place to terminate a water pipe.

no water pipe under the consumer, the pipe with plastic cap In picture is the bottom of my ironing board

The unused cores are not terminated safely to avoid inadvertent contact, and the use of 4 core is redundant, but could have usefully used the cores in parallel.

not sure what you mean on the last part, do you mean I could double the wires up? Connect the two unused ones to the ones being used?

The electrical work done in the garage requires extensive inspection, testing and certification and legally requires notification to building control, these may have been done but I am not certain of that from your description.
Based on the previous work done the installation in the garage is a TT system which requires a quality level of earth from the external rod and if this was DIY done then it is unlikely to be well done and may present a danger to the installation.


I am assuming the green and yellow cable running beside the CU and RCD is going to the rod and not to the SWA armour, if it is from the armour then the system may not be TT in its entirety and would change the requirements for the installation.

Wire comes from consumer to earth rod, garage end of armour does not have an earth attached to it

The use of C type RCBOs in this situation may, based on the design of the installation, cause problems with compliance with the disconnection times for a short circuit, though the earth fault levels would be complied with by the use of the RCD parts, if the rod is suitable.
The cables for the 16A sockets do not appear to be sealed into the sockets which could allow contamination into the socket cable connections.

There are rubber grommets on the top of the 16a sockets

That is all I can anticipate at the moment, some of them may not be correct as I cannot assess the installation, but they do give rise to concern.

Hello. Have answered what I can.

 

[coticsam]

What is the going rate to have a company come out a test/ diagnose this? Anyone in the suffolk area care to help?

 

[Richard Burns]

Good answers, I have made some wrong assumptions there, so not as bad as I thought.
Chedburgh is a little too far for me, but someone else may be able to assist.

 

[coticsam]

After speaking to my dad last night he gave me the number of an electrican he has done some work for before, he came over today to have a look. He fitted a 32a rcbo and wired one of my 16a sockets into that, while I was welding with power on max he measured amps, peak amps the welder was drawing was 22a on max. He said the rcbo on this circuit is not needed as I have a rcb before consumer unit so have double protection? I have been advised to replace with a 20a mcb type d to help with input rush

 

[telectrix]

After speaking to my dad last night he gave me the number of an electrican he has done some work for before, he came over today to have a look. He fitted a 32a rcbo and wired one of my 16a sockets into that, while I was welding with power on max he measured amps, peak amps the welder was drawing was 22a on max. He said the rcbo on this circuit is not needed as I have a rcb before consumer unit so have double protection? I have been advised to replace with a 20a mcb type d to help with input rush

you could run into excessive loop impedance with a 20A type D. i'd leave well alone if it's working OK.